Davies



(No Model.)

2 SheetsSheet 1. W. LANGDON-DAVIES. ELEGTROMAGNBT HAVING ROTATINGFIELDS. N0. 60 4,0 55.

Patented May 17,1898.

(No Model.) 2 Sheets-Sl1eet 2.

W. LANGDON-DAVIES.

BLEGTROMAGNBT HAVING ROTATING FIELDS.

No. 604,055. Patented May 17,1898.

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UNITED STATES PATENT OEEIcE.

IVALTER LANGDON-DAVIES, OF LONDON, ENGLAND, ASSIGNOR, BY MESNEASSIGNMENTS, TO THE DAVIES MOTOR COMPANY, LIMITED, OF SAME PLACE.

ELECTROMAGNET HAVING ROTATING FIELDS.

SPECIFICATION forming part of Letters Patent No. 604,055, dated May 17,1898.

Application filed May 28, 1896. $erial No. 592,831. (No model.)

To all whom it may concern: I to one another at an angle which is thesup- Be it known that I, WALTER LANGDON- plement of the phase anglebetween the fields DAVIES, a subject of the Queen of Great they producea uniforoily-rotating resultant Britain, residing at 57 Oomeragh road,Vest of constant strength.

5 Kensington, London, in the county of Mid- I have also found that whenthe axes of any dlesex, England, have invented certain new two simpleharmonic fields differing in phase and useful Electromagnets HavingRotating are inclined one to the other at an angle which Fields, ofwhich the following is a specificais the supplement of the phase anglebetween tion. the fields they will produce the closest ap- [o In myprior application, filed November 7, proximation to a uniformly-rotatingresultant 1895, Serial No. 568,201, there are described field ofconstant strength. It is therefore 60 means by which an alternatingsingle-phase correct to place the axes of these fields at current may bemade to produce a rotary ninety degrees when the phase difference ismagnetic field suitable for a self-starting alninety degrees between thetwo fields. I have 15 ternating-current motor and suitable also fordiscovered, however, that when the difference atransformer whichisrequired to transforma is not ninety degrees the axes of the fieldssingle-phase current into two approximately should be inclined to eachother at an angle equal currents differing from one another in which isthe supplement of that angle by phase. For these purposes, whether it beto which the magnetization of the two fields 2o obtain the greateststarting moment in an differ in phase. In general the difference ofelectromotor or the greatest efficiency in a phase to be taken intoconsideration for the transformer, the magnetic field should rotateabove purpose will be that which exists inias uniformly as possible andshould not vary tially; but if it is intended that the motor instrength. The means described in the said shall run asynchronously, aswell as to be 25 specification approximately satisfy these conthus setin motion, it may be found advanditions, but greater uniformity may beobtageous to take the difference of phase when tained. the motor is ator about its normal work. It

I have demonstrated that when two fields is also importantthat themagnetic flux should are used to produce the rotating field the coils beas evenly distributed over the polar sur- 0 should be so set that theaxes of the two fields faces as possible. Now, supposing an annularproducing the resultant rotating field are in field-magnet and acylindrical rotormounted 8o clined to each other at an angle which isthe within it, the axis of the field generated by supplement of thatangle by which the curthe field-magnet through the rotor being verrentsin the two coils differ in phase. Thus, tical, then this field may berepresented by a 3 5 supposing the phase difference of the currentsnumber of vertical lines drawn across the anin the coils to beforty-five degrees, (which is nular field-space, and these lines, whichwill 8 5 about the maximum dilference of phase which decrease in lengthfrom the center line or diis suitable and is readily obtained from oneameter to either side, will approximately rep- I electromotive source,)the coils should be so resent the reluctances of the magnetic paths 0set upon the core that the north pole of one across the various elementsof the field. If

field is one hundred and thirty-five degrees now the same magnetomotiveforce be apfrom the north pole of the other field. Thus plied over thewhole field by surrounding the two equal fields having simple harmonicvafield-space with a single coil, a stronger magriations which are notin phase with one annetic field will be generated through the reotherare combined to produce a rotary field gions of lesser reluctance, andas a result the of which both the strength and the velocity of fieldgenerated by the above-described field- 5 rotation are constant. magnetwill be considerably denser at the two The law is general that when theaxes of sides than in the center.

two equal simple harmonic fields are inclined Figure 1 illustrates theusual method of applying a winding to a cylindrical field-magnet andindicates the nature of the magnetic field so obtained. Fig. 2illustrates the usual method of applying two windings when a rotatingfield is required. Fig. 3 illustrates the new method of winding asapplied to the production of a single alternating field. Fig. 3 is adiagram by the aid of which the proper distribution of the winding isascertained. Fig. at is a modification of Fig. 3. Fig. 5 is anexplanatory diagram. Fig. 6 illustrates another modification, in whichthe winding is divided into equal sections and the holes to receive itare not equally spaced. Fig. 7 illustrates the winding of a four-polefield-magnet, the winding being divided into equal sections. Fig. '7explains the winding of a four-pole field-magnet, the holes beingequally spaced. Figs. 8 and 9 illustrate the winding for a rotatingfield, in which the two component fields are at right angles, and thedifference between the phases of the currents is also ninety degrees.Fig. 10 illustrates the winding for a rotating field where thedifference between the phases of the currents is fortyfive degrees. Fig.10 represents the currents in the two field-windings displacedforty-five degrees in phase. Figs. 11, 12, and 13 show the rotor which Iemploy.

Fig. 1 shows an end view of an iron cylinder such as would be used in amotor wound with a single coil to produce a field perpendicularly acrossthe interior diameter. The conductors are wound through the holes at thesides of the cylinder, say up in a direction parallel with the axisthrough the hole on the left-hand side A, across the end of the cylinderin a semicircle, and down through the right-hand hole B, again in adirection parallel with the axis. Now with such a winding when thecurrent passes polarities ,N and S are obtained, but the field is not atall uniformly distributed for the reason already given namely, thedifferent reluctances of the pathsand the field is very dense at the twosides near A and B and diminishes very considerably toward the center,as is indicated by the figure. Now it is a fact (as might, indeed, beanticipated) that a uniform rotating field cannot be obtained bysuperposing, as in Fig. 2, two fields, such as Fig. 1 indicates, whichare not individually uniformly distributed.

Fig. 3 illustrates my method of winding, by which I obtain approximatelyuniform distribution in each of the individual component fields. Idistribute the winding so as to compensate the different reluctances ofthe paths. A portion only of the winding is threaded through the holes AB, while another portion is threaded through holes 0 D, and, it may be,a third portion through holes E F, and a fourth portion through holes GII. Then the windings O D E F G II will successively reinforce themagnetomotive force in those sections of the field which needreinforcement in conse quence of the progressive increase in thereluctance. The dotted lines indicate the directions taken by thewinding Wires in passfrom hole to hole.

The number of the sections into which the winding is divided may bevaried. Three will be sufficient for the smallest class of two-polemotors, and four or more sections will he used in two-pole motors oflarger size.

The cylinder is built up of thin disks of soft iron, having sixteenholes in each, and is adapted to receive two similar windings, one aboveand the other below the horizontal diameter of the cylinder as itappears in the figure, each winding being in four sections and similarlysituated. These windings above and below may be regarded as parts of asingle coil. It is not essential, however, that the windings should bethus arranged. There need be no winding on the lower part of thecylinder, or the lower part of the cylinder may be reserved to receive awinding for a current differing in phase to produce with the firstwinding a resultant field of different phase from the first, or, again,the winding on the lower half may be omitted and the upper winding maybe then redisposed, as in Fig. 4, partly on the upper and partly on thelower half of the cylinder.

The rule by which I apportion the turns in the several sections for acylinder such as Fig. 3 is the following: Draw a figure such as Fig. 3,in which the points A B O D E F G H on the circumference of a circlecorrespond to the equally-spaced holes similarly lettered in Fig. 3.Bisect the intervals between the holes in points 1, 2, 3, 4-, and 5,marked on the circle. From the neutral point 1 draw a radius, and fromthe point 5 at the center of the polar surface draw another radius. Theymeet at the center 0 in a right angle. Draw a line 2 6, so that theangles at- 6 are right angles. Draw right angles 6 2 7, 2 7 3, 7 3 8, 38 4, and 8 e 9. Then the lengths of the lines 2 (5, 3 7, 4 8, and 5 9represent and are proportional to the numbers of turns which should bewound through the holes A B, O D, E F, and G H, respectively. Thus Ifind, for example, that if I wind through A B nineteen turns I shouldwind through OD sixteen turns, through E F ten turns, and through G Hfive turns, these being the nearest whole numbers. I give to the windingGII the advantages of fractional parts. Similarly I calculate when thenumber of sections is less or greater than four.

The rule given above is readily deduced from the fact that thereluctance of two paths (represented in Fig. 5 by lines 3 and Variesapproximately as the sines of the angles Y and Z. I therefore apply aproportionately greater magnet-motive force about than along 1/.

It will be observed that neutral intervals occur between the upper andthe lower windings. It is expedient to provide in this manner forneutral areas between the polar surfaces.

'ameter of the armature-space.

When the total number of turns to be wound on is but small, sufficientaccuracy cannot be obtained with equally-spaced holes. I then prefer toWind an equal number of turns in each section and to vary the distancesbetween the holes. Such a field-magnet may be set out in the mannershown in Fig. 6. The diameter of the armature-space coinciding with theaxis of the field is divided into twice as many equal parts as there arecoils to be wound,(in this case sixteen.) At right angles to the axis ofthe field are drawn parallel lines through the points 2 4t 6 8 1O 12 14;16, cutting the di- Through the points where these lines cut thediameter are drawn radii, and the holes for winding are punched uponthese radii. As shown, these holes are bisected by the radii. I can in asimilar manner wind a-cylindrical magnetcore so as to obtain four ormore poles. Fig. 7 shows a cylinder prepared to receive a fourpolewinding.

In the case of afour-pole magnet when the holes are equally spaced andthe number of turns on the coils differ from one another, as in Fig. 3,I ascertain the proportions to be given to the several sections of thewindings by drawing a diagram such as Fig. 7. It is very similar to Fig.3; but now the radii 5 O and O 1 meet in an angle of forty-five degrees.In other respects the description of Fig. 3 applies.

I have up to this point assumed that the air-space between the polarsurfaces of the magnets Was free from iron. It is, however, at onceobvious that the introduction of the iron rotor or armature will alterthe problem only in degree and not in method of solution. The presenceof the iron rotor does not alter the conditions except by lessening thetotal amount of the magnetic reluctance. Whether in iron or in air thelonger course has the greater reluctance.

I have so far described the winding for obtaining one uniform field. Toyield a rotating field, a second winding is required, separated from thefirst winding by an angular distance dependent on the diiference ofphase in the two windings, as already explained. I can apply the secondwinding over the first, using the same holes, or some of them, toaccommodate both the windings. Thus in Fig. 8 the full lines show acylinder set out with holes for winding, as in Fig. 6, except that inthis case the windings are to be each in five sections. The dotted linesshow the holes repeated at ninety degrees distance from the holesrepresented by the full lines. The phase difference between the currentsin the coils is in this case assumed to be ninety degrees. It isobviously impracticable to punch the double set of holes as they occurin this diagram. Fig. 9 shows the arrangement of holes suit able toreceive two windings, the one over the other and at right angles. Thedotted lines crossing the central space represent diagrammatically onepair of windings and the dotted lines outside the central spacerepresent the other pair of windings.

Fig. 10 shows the arrangement which is suitable for a motor in which thedifference of phase in the two component fields is forty-five degreesand in which the current in the two coils is derived from the samesource, the coils being adjusted to equal ampere-turns in the mannerdescribed in my before-mentioned application. The winding havingterminals a a is placed, as shown, with its magnetic axis inclined onehundred and thirty-five degrees to the winding having the terminals b b.The variation in the number of turns is indicated by the varyingthickness of the lines representing the windings.

Fig. 10 shows the currents in the two fieldwindings displaced forty-fivedegrees in phase. Thus the magnetic axes of the two windings areinclined to each other at an angle, (one hundred and thirty-fivedegrees,) the supplement of the angle (forty-five degrees) representingthe difference in angles of lag of the currents in the two windings.

Figs. 11, 12,and 18 show a rotor which is suitable for use withfield-magnets such as herein described. It consists of a series of irondisks threaded upon a shaft A and clamped fast between screw-nuts B. Afeather O prevents the disks from turning on the shaft. A series ofcopper rods D are passed through the disks and at their ends are fixedinto massive copper rings E. Saw-cuts are made in the edges of the disksparallel to the axis and penetrating into the holes which receive thecopper rods. These slits are seen in Fig. 13. The thick black lines inFig. 11 indicate in sulating material.

Field-magnets in accordance with this invention are also applicable totransformers.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is 1. An electromagnet energized from a single source ofalternating electromotive force comprising two component fields of equalrates of alternation but with different phase angles of magnetization,having their magnetic axes inclined one to the other at an angle otherthan ninety degrees and equal to the supplement of that angle by whichthe currents in the two component windings differ in phase, thusproducing a rotary field.

2. A11 electromagnet energized from a single source of alternatingelectromotive force, for an electric motor or transformer, comprisingtwo component fields of equal strength and equal rates of alternation,but with different phase angles of magnetization, having their magneticaxes inclined one to the other at an angle other than ninety degrees andequal to the supplement of that angle by which the currents in the twocomponent windings differ in phase, so as to produce a resulting rotaryfield of constant strength and of uniform rate of rotation.

3. A field-magnet for an electric motor or transformer, consisting of asubstantially cy lindrical magnetic core, wound with coils of wireencircling varying amounts of the cylindrical field-space, the coilsbeing distributed upon the cylinder in due proportion to the magneticreluctance to be overcome in the central field-space, so as to produce afield of substantially uniform density, substantially as described.

4:. A field -magnet for electric motors or transformers consisting of asubstantially cylindrical magnetic core,wound with two componentwindings,with their axes of magnetization inclined one to the other,each winding being composed of coils of wire encircling Varying amountsof the cylindrical field-space, the coils being distributed upon thecylinder in due proportion to the magnetic reluctance to be overcome inthe central field-space, so as to produce aresultant field ofsubstantially uniform density, substantially as described.

5. A field-magnet for electric motors or transformers, consisting of asubstantially cylindrical magnetic core,wound with two componentwindings, carrying currents of different phase, the magnetic axes of thetwo component fields being inclined one to the other, each winding beingcomposed of coils of wire encircling Varying amounts of the cylindricalfield-space, the coils being distributed upon the cylinder in dueproportion to the magnetic reluctance of the central field-space, so asto produce a rotary field of substantially uniform density,substantially as described.

6. A fieldmagnet for electric motors or transformers consisting of asubstantially cylindrical magnetic core,wound with two componentwindings, carrying currents of equal magnetizing effects and rate ofalternation but of different angles of lag, the magnetic axes of the twocomponent fields being inclined one to the other at an angle equal tothe supplement of that angle by which the currents in the componentwindings differ in phase, each winding being composed of coils of wireencircling varying amounts of the cylindrical fieldspace, the coilsbeing distributed upon the cylinder in due proportion to the magneticreluctance to be overcome in the central field-space, so as to produce aresultant rotary field of uniform density, constant strength, anduniform rate of rotation.

'7. An electromagnet having a rotating field resulting from two windingscarrying currents differing in phase asymmetrically arranged upon thecore and inclined the one to the other at an oblique angle which is thesupplement of the angle by which the current in the two windings differin phase.

lVALTER LANGDON-DAVIES.

\Vitnesses:

DEANSTON OARPMAEL, WILFRED OARPMAEL.

